relates to a method and apparatus for interfolding webs and more particularly for providing discrete stacks each having the same number of web segments--each segment being "V" folded to provide a pair of panels, the segments being offset one panel length.
Interfolding has been practiced for a long time--whereby the removal of one web segment automatically places the succeeding web segment in a position for manual grasping. As such, it has been widely used for both paper towels and facial tissue. Interfolded tissues, for example, have been made in two ways. One way was to fold longitudinally 200 webs, then severing the stack. This had the drawback of dispensing the tissues in the weaker cross machine direction. The other way was to transversely interfold (normally by tuckers and grippers) two webs so that the dispensing was in the stronger machine direction. It is to the latter way that the instant invention is directed.
In transverse zig-zag folding, there has been a problem of separating one stack from another. This is true irrespective of whether the webs are transversely perforated--as in tissues or whether the webs are transversely severed--as in towels.
In the case of the tissues, the perforations result in small bonds connecting contiguous segments. Therefore, such webs are essentially continuous. When a predetermined "count" was reached, some means had to be provided for isolating the already achieved count from the web material continuing to issue from the interfolder. This normally was done manually--with markers of some type being inserted to indicate the place of separation. This was both back-breaking and costly. Further, the breaking of the bonds could disarrange the bottom segment.
In the case of towels, separator plates were inserted from opposite sides of the stack to flank the ending and beginning panels of succeeding stacks. When these plates were separated as by lowering the lower plate faster than the upper plate, the sheets became de-lapped. But, in doing this there was also the possibility of disarrangement because the segments were not under full control.
According to the instant invention, the stack separation is achieved by developing a spacing in the two continuous streams of contiguous web segments prior to the zig-zag folding. This spacing is achieved by reverse folding once each count the leading free edge of the leading segment of each stream.
Separation of segments or sheets prior to zig-zag folding has been performed previously, but not for use with a single folder. In both U.S. Pat. No. 4,494,741 and co-pending, co-owned application Ser. No. 816,441 filed Jan. 6, 1986, the separation was achieved for directing the web streams alternately to a pair of folders. More importantly, there was no suggestion of achieving the spacing by reverse folding.
The invention brings about additional advantages. Not only is the spacing between stacks achieved but further the reversely folded portion of the protruding web provides a starter tab for manual grasping to remove the web segments from a container and further, the reverse folding also provides a multiple thickness, longitudinally extending web portion to facilitate the zig-zag folding of the initial panel of a stack.